This application claims the benefit of Australian Provisional Application filed on Nov. 13, 1998.
1. Field of the Invention
The applicant is knowledgeable of the design and operation pulverizing mills used to grind mineral samples into a fine powder. The pulverizing mill together with many other types of machines require an orbital or vibratory motion in order to work. These machines include for example screens for screening particles, cone crushers for crushing rocks, and shakers and stirrers for shaking and stirring laboratory solutions, biological/medical products and specifications, and the like.
2. Related Art
Traditionally, the orbital or vibratory motion required on such machines is imparted to an object by attaching the object: to a spring mounted platform to which is coupled an eccentrically weighted shaft driven by a motor: or, via bearings to an eccentric shaft driven by a motor. A mechanical coupling such as a gear box, belt, or universal joint is used to couple the output of the motor to the shaft.
However, the very motion that these machines are designed to produce also leads to their inevitable and frequent failure. Specifically, the required orbital or vibratory motion leads to fatigue failure in various components of the machines including mechanical couplings, transmissions, bearings, framework and mounts. The cost of repairing such failures is very high. In addition to the cost of repairing the broken component(s) substantial loses can be incurred due to down time in a larger process in which the failed machine performs one or more steps. A further limitation of such machines is that they produce fixed orbits or motions with no means of dynamic control (i.e. no means of varying orbit path while machine is running).
The present invention has evolved from the perceived need to be able to (generate orbital or vibratory motion without the limitations and deficiencies of the above described prior art.